<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>注册页面</h1>
<form action="">
    <input type="text" name="username" placeholder="用户名" onblur="fn()">
    <span></span><br>
    <input type="text" name="password" placeholder="密码">
    <input type="button" value="注册">
</form>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<script>
function fn() {
    // alert("编辑完成")
    //得到form表单的数据
    let data =new FormData(document.querySelector("form"));
    //发出异步请求
    axios.post("/check",data).then(function (response) {
        let span =document.querySelector("span");
        span.innerText=response.data;
    })
}
</script>

</body>
</html>